During the interview, May laughed off the president's legal action suggestion, saying she would carry on with negotiations, but added: "Interestingly, what the president also said at that press conference was "don't walk away". The president then used a news conference with May to walk back his previous comments, saying he understood that the advice he gave her was "a little bit tough".

"This is a good deal for the UK".

He added that it was "too bad what is going on", and that her ultra-soft Brexit plans would "probably kill" a British-American trade agreement by leaving the European Union with too much control over Britain's economy for a deal to be made.

On the prospects of a trade deal collapsing, he added: "I think it's worse for United Kingdom than it is for us because we're doing very well, and we're doing very well at trade, and we're doing incredibly well overall, and we're having the best numbers we've ever had as a country -best employment numbers, best GDP numbers".

She said such rules were needed to protect jobs in firms with supply chains that crossed borders and deal with the Irish border issue. But we should also prepare for no deal.

"I want us to be able to sit down to negotiate the best deal for Britain", May said.

"Everyone thought it was going to be "Oh it's simple, we join or don't join, or let's see what happens", he said.

"By working closely together, government and industry have ensured we remain at the forefront of civil aviation and that our air power is second to none", May will say.

The 104-page document calls for close economic ties with the bloc through a new free trade area, as well as a "common rulebook" for goods. Both of those are unacceptable.